1. Field of the Invention
The present invention concerns a hydrokinetic coupling appliance for a motor vehicle.
2. Description of Related Art
There is already known, in the prior art, for example according to the document WO 99/45294, a hydrokinetic coupling apparatus, in particular for a motor vehicle, of the type comprising:                a casing, intended to rotationally connect, about an axis X, a driving shaft and an impeller wheel,        a turbine wheel intended to be rotationally connected to a driven shaft,        a clutch for locking the coupling of the driving and driven shafts comprising a piston for disengageably connecting the turbine wheel to a substantially radial wall of the casing against which the piston is forced for the locking of the coupling, and        a friction stop interposed axially between the turbine wheel and the piston.        
In general terms, in such a hydrokinetic coupling appliance, the casing provided with a substantially radial wall constitutes the input element and the output element for its part consists of a turbine wheel/hub assembly housed inside the casing. The piston is located between the assembly and the wall and is mounted so as to be able to move axially with respect to the wall, whilst being rotationally connected thereto.
In a conventional manner, the turbine wheel is driven by the impeller wheel by virtue of the circulation of a fluid, such as oil, contained in the casing.
In the case of a hydrokinetic coupling appliance for a motor vehicle, the driving shaft is the output shaft of the vehicle engine and the driven shaft is connected to gear ratio change means. After the vehicle is started, the locking clutch, also referred to as a “lock-up” clutch, controls the slip between the turbine and impeller wheels by controlling the driving of the driving shaft connected to the casing by the driven shaft connected to the turbine wheel. This drive control of the shafts is effected by clamping an annular friction disc arranged between the piston and the locking wall of the casing.
The connecting wall of the hub illustrated in this document comprises a substantially radial plate, made from the same material as the hub, and a damper plate connecting this hub to means of coupling the hub and friction disc with circumferential damping. The turbine is also connected to the plate of the hub. A bracing member, in the form of a flat ring, is interposed axially between the plate of the hub and the piston and forms a friction stop in order to prevent direct contact between this plate and this piston.